The prior art knows what are known as microbial mandelate racemases, which are capable of racemizing mandelic acid in vitro or in vivo (G. L. Kenyon, J. A. Gerlt, G. A. Petsko and J. W. Kozarich, “Mandelate Racemase: Structure-Function Studies of a Pseudosymmetric Enzyme”, Accts. Chem. Res., 28, 178-186 (1995); R. Li, V. M. Powers, J. W. Kozarich and G. L. Kenyon, “Racemization of Vinylglycolate Catalyzed by Mandelate Racemase”, J. Org. Chem., 60, 3347-3351 (1995); S. S. Schafer, A. T. Kallarakal, J. W. Kozarich, J. A. Gerlt, J. R. Clifton and G. L. Kenyon, “Mechanism of the Reaction Catalyzed by Mandelate Racemase: The Structure and Mechanistic Properties of the D270N Mutant”, Biochemistry, 35, 5662-5669 (1996)).
At the same time, the simple production of chiral, nonracemic substances, for example for the production of active ingredients in the pharmaceuticals industry, is greatly needed. The enzyme-catalyzed racemization of a stereoisomeric form of a compound, which leads to the desired enantiomer, would constitute a suitable route for producing the desired, chiral, nonracemic materials. However, the racemases known to date are distinguished by their high substrate specificity. Thus, mandelate racemase is only suitable for the biocatalytic racemization of beta,gamma-unsaturated alpha-hydroxyacids. Saturated alpha-hydroxycarboxylic acids are not accepted (cf. Felfer, U. et al., J. Mol. Catal. B: Enzymatic 15, 213 (2001)).